Impact resistant door facing, method of forming impact resistant door facing and door formed therewith

ABSTRACT

The present invention is directed to an impact resistant door facing. The facing includes a rectangular sheet of molded hardened polymeric material having first and second opposing major surfaces. A mat having a continuous structure is integrally molded into the sheet. The mat is sufficiently porous to allow the polymeric material to permeate the mat prior to the polymeric material having hardened. The mat is disposed within the sheet so that at least one of the major surfaces is unbroken. The present invention also relates to a method of forming the disclosed door facing, and a door formed therewith.

CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM TO PRIORITY

This application is based on provisional application Ser. No.60/612,251, filed Sep. 23, 2004, for Manish Gupta et al, the disclosureof which is incorporated herein by reference and to which priority isclaimed under 35 U.S.C. § 120.

FIELD OF THE INVENTION

The present invention is directed to an impact resistant door facing.The facing includes a rectangular sheet of molded hardened polymericmaterial having first and second opposing major surfaces. A mat having acontinuouse is integrally molded into the sheet. The mat is sufficientlyporous to allow the polymeric material to permeate the mat prior to thepolymeric material having hardened. The mat is disposed within the sheetso that at least one of the major surfaces is unbroken. The presentinvention also relates to a method of forming the disclosed door facing,and a door formed therewith.

BACKGROUND OF THE INVENTION

As known in the art, door facings may be secured to a support structureor frame to form a hollow core door. Such facings may be molded from apolymeric material, such as sheet molding compound (“SMC”). SMC may bemolded to form a door facing including one or more depressions orgrooves, such as one or more square or rectangular depressions. Thesedepressions may define the perimeter of one or more simulated panels.Alternatively, the facings may be flush.

The door facings are secured to opposing sides of the frame, forminghollow spaces between the facings. A core component or material issometimes used to fill the hollow spaces. Conventional core materialsfor use in hollow core doors include corrugated cardboard, paper, foam,or fiberboard.

It is sometimes desirable to provide an exterior door that can withstandimpacts from flying debris, such as in a high velocity wind zones. Doorsare sometimes required to pass certain performance tests, such as thosedeveloped by the American Society of Testing Materials (ASTM) which testthe performance of doors exposed to the effects of windstorms and impacttesting. Doors may also be required to meet regional performance testswithin a particular state, such as the Dade County, Florida, hurricaneimpact test. The Dade County test requires that the inner door surfacehave a crack, if at all, smaller than 1/16 inch by 6 inches.

Various attempts have been made to provide a hollow core door that canwithstand impact testing. One design provides a hollow core door havinga mat disposed within the door cavity and between the opposing doorfacings. A cementitious material is poured around the mat. Such doorsare relatively expensive and difficult to assemble. In addition, theyare relatively heavy, and therefore difficult to store, transport andinstall. Other designs provide for metal door facings. Such doors arealso relatively expensive. In addition, they are often less desirable toconsumers because they lack aesthetic detail, and may rust and dent.

Therefore, there is a need for an impact resistant door that overcomessome or all of the above noted problems and disadvantages.

SUMMARY OF THE INVENTION

The present invention is directed to an impact resistant door facing.The facing includes a rectangular sheet of molded hardened polymericmaterial having first and second opposing major surfaces. A mat having acontinuous structure is integrally molded into the sheet. The mat issufficiently porous to allow the polymeric material to permeate the matprior to the polymeric material having hardened. The mat is disposedwithin the sheet so that at least one of the major surfaces is unbroken.

An impact resistant door is also disclosed. The door includes aperipheral frame, and first and second door facings secured to opposingsides of the frame. At least one of the facings comprises a rectangularsheet of molded hardened polymeric material having first and secondopposing major surfaces. A mat having a continuous structure isintegrally molded into the sheet. The mat is sufficiently porous toallow the polymeric material to permeate the mat prior to the polymericmaterial having hardened. The mat is disposed within the sheet so thatat least one of the major surfaces is unbroken.

The present invention also relates to a method of forming an impactresistant door facing. A die mold is provided having first and seconddies defining a cavity. A mat having a continuous structure is disposedwithin the cavity. A sheet of polymeric material is disposed on the mat.The mat and sheet are compressed between the first and second dies usingheat and pressure. The mat is sufficiently porous to allow the polymericmaterial to permeate the mat during the compression process, therebyforming a door facing having first and second opposing major surface anda continuous structure integrally molded into the sheet so that one ofthe major surfaces is unbroken.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an impact resistant door facingaccording to the present invention;

FIG. 2 is a cross-sectional view of a die mold with a sheet of polymericmaterial and mat disposed therein prior to compression;

FIG. 3 is an elevational view of an impact resistant door facing havingtwo integrally molded pieces of mat arranged in a cross configuration;

FIG. 4 is an elevational view of an impact resistant door facing havingthree integrally molded pieces of mat arranged in a Z configuration; and

FIG. 5 is a cross-sectional view of an impact resistant door having oneimpact resistant door facing.

DETAILED DESCRIPTION OF THE INVENTION

As best shown in FIG. 1, an impact resistant door facing 10 includes arectangular sheet 12 of molded hardened polymeric material having firstand second opposing major surfaces 14, 16. A mat 18 is integrally moldedinto the polymeric material. Mat 18 is preferably woven or knitted.Non-woven fabrics may be used, such as fiberglass felts, provided thatthey have a continuous structure to which the polymer may bind. Mat 18has a porosity sufficient to allow the polymeric material to permeatemat 18 prior to the polymeric material having hardened, but not so highas to cause the mat 18 to float within the mold cavity during thepressing step. Mat 18 is disposed within sheet 12 so that at least oneof major surfaces 14 is unbroken, thus providing a surface having asurface finish and quality suitable for the exterior surface of a door.

The polymeric material used to form sheet 12 is preferably ansheet-molding compound (“SMC”), such as from unsaturated polyesterresin, having at least about 10% by weight chopped fiberglass and up toabout 18% by weight chopped fiberglass. Mat 18 is preferably a woven orknitted fiberglass fabric having a weight of at least about ten ouncesper square yard. The thickness of mat 18 may vary depending on theultimate thickness of sheet 12, but is preferably between about 0.0005inch and about 0.0015 inch. Suitable fiberglass fabrics for use in thepresent invention are commercially available. For example, Owens Corningmanufactures knitted fiberglass matting with a weight of 10 oz./sq. yd.Hexcel manufactures an E-glass fabric with 11 oz/sq. yd. While we preferthe use of fiberglass for the mat 18, other reinforcing filaments may beused to form mat 18.

Mat 18 may be pre-treated with an adhesive resin, or impregnated with anSMC paste. It is somewhat easier to handle and cut the fibrous materialof mat 18 when it is impregnated with resin or paste. The SMC pastepreferably comprises unsaturated polyester resin, filler, such ascalcium carbonate, and a catalyst, such as a peroxide. Preferably, theviscosity of the paste is about 40 million centipoise or less. The SMCpaste is preferably fiberglass free. Mat 18 is preferably includes asufficient amount of adhesive resin or paste to fully wet out mat 18.

The weave or porosity of mat 18 may vary depending on the viscosity ofthe SMC paste. Mat 18 should be sufficiently porous to allow thepolymeric material to permeate mat 18 and wet the fibers thereof priorto the polymeric material having hardened. Preferably, mat 18 has aweave finer than about 5 by 5 pics per square inch, more preferably mat18 has a weave of 10 by 10 pics per square inch. As the viscosity of theSMC is increased, the weave of mat 18 may become more course.

Mat 18 is integrally molded into sheet 12 during formation of facing 10.As best shown in FIG. 2, a die mold 30 is provided which includes upperand lower dies 32, 34 defining a cavity 36. Mat 18 is disposed withincavity 36. One or more strips of SMC material are positioned on top ofmat 18 within the mold cavity formed by dies 32,34. The SMC stripspreferable are about 6 inches wide and about 50 inches long. The numberand orientation of the SMC strips is a function of the size andconfiguration of the sheet 12 to be created. Mat 18 and the SMC stripsare compressed together between upper and lower dies 32, 34 using heatand pressure. Preferably, cavity 36 is maintained at a temperature ofbetween about 275° F. and about 350° F. during the compression process.Dies 32, 34 preferably exert a pressure on mat 18 and the SMC strips ofat least about 2800 tons pressure per square inch, more preferably atleast about 3200 tons pressure per square inch.

During compression, the polymeric material is caused to flow throughoutthe mold cavity created by dies 32,34. The porosity of mat 18 issufficient to allow the softened polymeric material to permeate the matduring compression, wet the glass fibers, and thereby be able to bind tothe fibers of mat 18. In this way, the polymeric material flows aroundthe fiberglass structure comprising mat 18. However, the weave of mat 18is also sufficiently fine, and the compression process is controlled,such that mat 18 is not pressed through first major surface 14. Rather,first major surface 14 is unbroken by mat 18, thereby ensuring adesirable surface quality of facing 10. Using the exemplary compressionparameters herein, the SMC strips and mat 18 may be compressed in mold30 for about fifty seconds.

Alternatively, mat 18 may be adhesively secured to second major surface16. Preferably, mat 18 is impregnated with an SMC paste, as describedabove. A sufficient amount of heat and pressure are applied to mat 18and sheet 12, so that the SMC paste in mat 18 is integrally bonded withthe polymeric material of sheet 12. In this way, the continuousstructure of mat 18 is also intimately bonded to sheet 12.

Mat 18 may have dimensions substantially the same as sheet 11 With somemolding equipment, it is may be advantageous to provide a mat 18 havingdimensions slightly smaller than the dimensions of the sheet 12, forexample mat 18 may have perimeter edges that are spaced from theperimeter edges of sheet 12. In this way, the edges of sheet 12 may beeasily cut using conventional molding equipment, given it is sometimesmore difficult for the molding equipment to cut through the fiberglassmat 18.

Facing 10 may include one piece of mat 18 molded into sheet 12.Alternatively, two or more pieces of mat 18 may be molded into sheet 12.For example, two pieces of mat 18 may be arranged in a crossconfiguration in sheet 12 as best shown in FIG. 3, or three pieces ofmat 18 may be arranged in a ‘Z’ configuration in sheet 12 as best shownin FIG. 4. It should be understood that mat 18 may have any shape ordimensions, and any number of pieces of mat 18 may be used and arrangedin various configurations, so long as mat 18 is integrally molded into asufficient portion of facing 10 so that stresses are dissipatedthroughout a substantially portion of facing 10.

The resulting door facing 10 has a significantly higher impact strengthcompared to conventional polymeric facing lacking the continuousstructure of mat 18. Facing 10 is impact resistant under ASTM testmethods and the Dade County, Florida hurricane test because mat 18dissipates stresses from impacts to first major surface 14 due to itscontinuous structure, which distributes the force of impacts over theentire surface of facing 10. The surface 14 is thus an engineeredstructure that dissipates energy arising from impacts, such as impactsattributable to hurricanes.

An impact resistant door 50 may be formed using at least one impactresistant facing 10, as best shown in FIG. 5. Door 50 includes aperipheral frame 52, at least one impact resistant door facing 10secured to one side of frame 52, and a second door facing 54 secured tothe opposing side of frame 52. If door 50 includes only one impactresistant facing 10, door 50 should be installed such that facing 10 isexteriorly disposed to the environment. Alternatively, second doorfacing 54 may also be an impact resistant door facing, such as facing10. Door 50 is impact resistant under ASTM test methods and the DadeCounty, Florida hurricane standards because facing 10 on door 50dissipates impact energy across its entire surface as described above.

Door 50 may also include a core material or component disposed betweenfirst and second facings 10, 54. Note that door 50 may have asubstantially planar exterior surface (i.e. a flush door), or includecontoured portions C simulating door panels, as shown in FIG. 5.Accordingly, mat 18 is sufficiently flexible so that it may beintegrally molded into sheet 12 even in contoured portions C. Exteriorlydisposed surfaces, including first major surface 14 of facing 10, mayinclude a textured or decorative surface, such as a wood grain patternthereon.

Certain aspects of the present invention have been explained withrespect to specific embodiments. However, it will be apparent to one ofordinary skill in the art that various modifications and variations canbe made in construction or configuration of the present inventionwithout departing from the scope or spirit of the invention. Therefore,it is intended that the present invention cover all such modificationsand variations, provided they come within the scope of the followingclaims and their equivalents.

We claim as follows:
 1. An impact resistant door, comprising: aperipheral frame defining an outer edge of the door; first and seconddoor facings secured to opposing sides of said frame; and a core portionof the door defined between the first door facing and the second doorfacing, at least one of said door facings comprising a hardenedrectangular sheet and a porous mat, the hardened rectangular sheetcomprising a sheet molding compound establishing an outer major surfaceof the at least one door facing, the outer major surface being unbrokenby the porous mat, the porous mat comprising woven fiberglass having acontinuous structure integrally molded into and permeated by the sheetmolding compound, the porous mat being directly adjacent to the coreportion of the door.
 2. The door of claim 1, wherein the hardenedrectangular sheet comprises sheet molding compound pre-impregnated intothe porous mat.
 3. The door of claim 1, wherein the hardened rectangularsheet is compression molded.
 4. The door of claim 1, wherein the porousmat has a weave finer than 5 by 5 pics per square inch.
 5. The door ofclaim 1, further comprising a core material disposed within the coreportion of the door defined between the first and second door facings.6. The door of claim 1, wherein the sheet molding compound is formedfrom a paste comprising an unsaturated polyester.
 7. The door of claim1, wherein the sheet molding compound comprises fiberglass
 8. The doorof claim 1, wherein the sheet molding compound comprises at least about10% by weight chopped fiberglass.
 9. The door of claim 8, wherein thesheet molding compound comprises between about 10% by weight and about18% by weight chopped fiberglass.
 10. The door of claim 1, wherein thedoor facings have rectangular outer boundaries that extend to andterminate at the peripheral frame.
 11. An impact resistant door,comprising: a peripheral frame defining an outer edge of the door; firstand second door facings secured to opposing sides of said frame; and acore portion of the door defined between the first door facing and thesecond door facing, a first door facing comprising a first hardenedrectangular sheet and a first porous mat, the first hardened rectangularsheet comprising a first sheet molding compound establishing a firstouter major surface of the first door facing, the first outer majorsurface being unbroken by the first porous mat, the first porous matcomprising first woven fiberglass having a first continuous structureintegrally molded into and permeated by the first sheet moldingcompound, the first porous mat being directly adjacent to the coreportion of the door, and a second door facing comprising a secondhardened rectangular sheet and a second porous mat, the second hardenedrectangular sheet comprising a second outer major surface being unbrokenby the second porous mat, the second porous mat comprising second wovenfiberglass having a second continuous structure integrally molded intoand permeated by the second sheet molding compound, the second porousmat being directly adjacent to the core of the door.
 12. The door ofclaim 11, wherein the first and second hardened rectangular sheetcomprise first and second sheet molding compounds pre-impregnated intothe first and second porous mats, respectively.
 13. The door of claim11, wherein the first and second hardened rectangular sheets arecompression molded.
 14. The door of claim 11, wherein the first andsecond porous mats have weaves liner than 5 by 5 pics per square inch.15. The door of claim 11, further comprising a core material disposedwithin the core portion of the door defined between the first and seconddoor facings,
 16. The door of claim 11, wherein the first and secondsheet molding compounds are formed from pastes comprising an unsaturatedpolyester.
 17. The door of claim 11, wherein the first and second sheetmolding compounds comprise fiberglass.
 18. The door of claim 11, whereinthe first and second sheet molding compounds comprise at least about 10%by weight chopped fiberglass.
 19. The door of claim 18, wherein thefirst and second sheet molding compounds comprise between about 10% byweight and about 18% by weight chopped fiberglass.
 20. The door of claim11, wherein the door facings have rectangular outer boundaries thatextend to and terminate at the peripheral frame.